ransgender women (assigned 'male' at birth with a female identity) are an understudied group with HIV prevalence rates in the range of 22 to 68%. Public health intervention research has produced no theory- driven, evidence-based interventions for transgender women. The unique cultural context of transgender women creates distinct risk factors that require systematic investigation and then integration into culturally elevant, community-based approaches to intervention. This K08 application describes a comprehensive, ntegrated training and research plan designed to serve as a pathway to scientific independence and the expertise to develop and test an innovative and urgently needed intervention to improve health outcomes among a highly marginalized population disproportionately affected by the HIV epidemic. The following raining objectives are proposed: (1) to acquire expertise in the evaluation and application of theories of behavior change to marginalized populations; (2) to enhance skills in the use of mixed methods data collection and analysis, with an emphasis on techniques relevant to measurement development and theory testing; (3) to gain knowledge and experience with clinical trials methodology, including issues of sampling, randomization, design, protocol development, and ethics; and (4) to obtain training and experience in methods for developing, implementing, and evaluating culturally grounded, theory-driven HIV prevention interventions for transgender women. The specific research aims of the mentored original research are: (1) to describe the role of transgender women's unique cultural context on their HIV-related risk and protective factors; (2) to create new and to adapt existing quantitative measures to more accuratelyassess psychosocial dimensions and behavior relevant to transgender women's HIV risk and protective factors; (3) to identify psychosocial factors associatedwith HIV-related sexual and injection risk behaviors and protective factors among transgender women; and (4) to develop and test the feasibility and acceptability of a theory- driven, culturally grounded HIV prevention intervention for transgender women. RELEVANCE (See instructions): Transgender women (assigned 'male' at birth but identify as female) are an understudied and highly vulnerable group, with HIV prevalence rates in the range of 22 to 68%. Due to stigma and discrimination, they may seek affirmation in ways that increase risk. This project seeks to investigate unique risk factors to develop a culturally relevant HIV prevention intervention for these high-risk women. PROJECT/PERFORMANCE SIJE(S) (if additional space is needed, use